1. Field of the Invention
The present invention relates to ink jet recording apparatuses that print characters and patterns with a recording head to which ink is supplied from an ink tank. More particularly, the present invention is directed to an ink supply device.
2. Background Art
Ink jet recording apparatuses are designed to form dots on a recording medium by jetting ink droplets out of nozzle openings while supplying, from an ink tank, ink to pressure producing chambers that communicate with the nozzle openings and applying pressure to the pressure producing chambers so as to correspond to print data.
Since the ink jet recording apparatuses are designed to jet ink droplets by applying pressure to the pressure producing chambers, when bubbles enter into the pressure producing chambers, the pressure for jetting ink droplets is absorbed by the bubbles. As a result, the ink droplets cannot be jetted or the ink droplet flying speed is reduced, which in turn imposes the problem of impaired print quality and the like.
In order to overcome such problems, a cleaning operation is performed when the ink tank is replaced with a new one or when the print quality has been greatly impaired. That is, bubbles are removed by discharging the ink out of the recording head while sealing the recording head with a cap or the like and applying a negative pressure to the recording head from outside.
In order to remove the bubbles and maintain the print quality, the ink is usually contained in a degassed condition, and bubbles are caused to disappear by utilizing the high gas dissolubility of the degassed ink.
In order to maintain the degassed condition of the ink from factory shipment to the hands of users, the ink must be kept in a container made of a gas shielding material and, in addition, the container must be wrapped with a gas shielding film or the like. As a result, there exists a problem that the running cost of printing is elevated.